Our previous study indicates an increased permeability of the pulmonary and cardiac capillaries after circumflex artery ligation in anesthetized dogs. In the proposed research, we will investigate the mechanism of the increase and quantitate the extravascular water of lungs, heart, liver and skeletal muscle after four hours of acute myocardial ischemia. We will collect cardiac and pulmonary lymph. We will determine the volume flow rate, protein concentration and albumin and globulin fractions of lymph and plasma in groups of dogs: (a) non-ligated control dogs, (b) four hours of circumflex artery ligation, (c) circumflex artery ligation plus moderately inreased left atrial pressure. An increase in cardiac or pulmonary lymph flow rate and an increase in protein concentration of lymph will indicate an increase in microvascular permeability in animals after coronary artery ligation. Moreover, an increased albumin and globulin lymph: plasma ratio would indicate decreased sieving of large molecules after ligation. Continuous monitoring of pulmonary arterial, left atrial and aortic pressures, and periodic determination of pulmonary microvascular pressure and cardiac output will permit us to assess hemodynamic factors contributing to increased extravascular water content in acute myocardial ischemia. In this regard, our model of circumflex artery ligation produces no significant changes in steady-state vascular pressures. Thus, our studies will incorporate controlled increases in left atrial pressure. Results of these studies will quantitate changes in the extravascular water content of normal and ischemic tissue and provide information concerning the mechanism of edema formation in uncomplicated acute myocardial infarction and in myocardial ischemia with increased left atrial pressure.